A reader writes: “Your article on reading wine labels got me to wondering about sulfites in wine. As we understand the labeling situation, wine companies only need to use the statement "contains sulfites". My wife believes that different brands use different amounts of sulfite and prefers those that have the least. But actually, we have no way of knowing the amount unless the label specifically states that there are no sulfites used in the bottling of the wine. We would sure appreciate any information which you could send our way on finding the amount of sulfite used in various labels.”

The sulfite warning label on wines often seems to confuse consumers. Even among professionals, opinions and sometimes research about the effects of sulfites in wine don’t always agree. I have been told by authorities on the subject that sulfites do not and cannot cause wine headaches, and that very few people are genuinely allergic to sulfites. I have also been told that sulfites are naturally occurring, not just in wine, but in other food products as well, such as orange juice.

Most wines do have sulfites added, particularly during fermentation and bottling, to control oxidation and prevent spoilage. Any wine with a sulfite concentration of just 10 parts per million (ppm) is legally required to carry the warning label. There is no legal requirement, however, for any wine label to indicate the exact ppm in its wines. Wines labeled NSA (no sulfites added) will have the lowest percentage, but often have a shelf life measured in months rather than years. I know of no wines that are completely, 100% sulfite-free.

If a newly-opened wine bottle has a sharp, slightly burning scent, particularly of burnt matches, you are most likely getting a whiff of SO2 from the bottling process. That will blow off rather quickly with vigorous swirling and/or decanting.